Text in speech bubble Blender v.2.81a
If you want to add a text-object, switch to object mode.



Then press Shift+a and select the "Text"-option, to add a new text-object.

Because the new text-object is rotated by default, you may not see it from your perspective, so rotate it on the x-Axis by 90°. (r+x+90)



The text can be altered if you have it selected and press Tab, to enter edit mode, then change your text as in any text editor. Press tab again, to exit edit mode. Other text settings like the font can be found in the right side panel.